Over the past decades, underwater communication have evolved into a very active research area since it facilitates the needs of many military, or more recently, commercial operations. Applications that may require underwater communications include communications with submarines, communication between divers, command of autonomous underwater vehicles (AUV), animal tracking, sea bed exploration, pollution monitoring, remote control of off-shore equipment, data collection from deep sea sensors, and so on. These applications of underwater communication rely mostly on the transmission of acoustic waves. Several military, commercial and research implementations of acoustic communication systems exist that are capable of achieving high data rates at considerable range.
FIG. 1 illustrates an example of a deep sea underwater acoustic communications system 100. The acoustic communications system 100 is maintained below water level 102 and includes a typical transmitter 104 and receiver 106 pair. The transmitter 104 may include a transmitting communications protocol 108, which is responsible for enabling data transfers and for defining syntax, semantics, and synchronization of the communications. The transmitter 104 may also include an error correction algorithm unit 110. Many prior art error correction algorithm units employ frequency shift keyed (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM) schemes. These modulation schemes compensate digitally encoded data for distortion and noise introduced to data during transmission. Upon modulation from the error correction algorithm unit 110, the digital data is then converted to an analog signal via a digital to analog converter 112. The analog signal is then amplified by a power amplifier 114 A projector (i.e., transducer) 116 is typically used to transmit the acoustic data 118 underwater.
The receiver 106 includes a hydrophone (i.e., transducer) 120 for detecting the acoustic data 118 and a preamplifier 122 for amplifying received analog signal. An analog-to-digital converter 124 is used to convert the received analog signal to a digital signal. A receiving error correction algorithms unit 126 is used to demodulate the received signal using the inverse of methodologies similar to that of the transmitting error correction algorithm unit 110. Finally, the receiver 106 may also include a receiving communications protocol 128 similar to that of the transmitting communications protocol 108.